firmware update: http://swcdn.apple.com/content/downloads/58/23/091-01783/14xsasthu8pbgh5pu12i8ssx5ykvcz4klj/FirmwareUpdate.pkg
full bundle update: http://swcdn.apple.com/content/downloads/58/23/091-01783/14xsasthu8pbgh5pu12i8ssx5ykvcz4klj/FullBundleUpdate.pkg
embedded os firmware: http://swcdn.apple.com/content/downloads/58/23/091-01783/14xsasthu8pbgh5pu12i8ssx5ykvcz4klj/EmbeddedOSFirmware.pkg
And to use the packages, it depends which partition you install from.
To install from same partition
1. Start update via mac app store
2. Move packages into /Library/Updates/091-01783 for the delta or /Library/Updates/091-01782 for the combo
3. Restart.
4. Go to updates tab in mac app store and click update
To install from different partition with El Capitan (for computers which can still be booted up by el capitan)
Just run the packages individually, carefully selecting the Sierra partition on which to install.
(El Capitan is still available in mac app store at https://itunes.apple.com/app/os-x-el-capitan/id1147835434?mt=12 )
